Traffic Experiments -- How to clear traffic jams(eskimo.com)
eskimo.com
Traffic Experiments -- How to clear traffic jams
http://www.eskimo.com/~billb/amateur/traffic/trafexp.html
23 comments
Pretty sure transmission type has nothing to do with it -- traffic is stop and go in plenty of places where most cars have manual transmissions.
I'm increasingly convinced that it's due to so many drivers optimizing for local minima, at the expense of not just everyone around them, but of themselves thirty seconds later.
I'm increasingly convinced that it's due to so many drivers optimizing for local minima, at the expense of not just everyone around them, but of themselves thirty seconds later.
Duh, I meant local maxima, of course -- at least, that's what those drivers are trying for. What they get most of the time are more like minima, of course.
I am pretty sure this is one of the many reasons. I recently came to usa from eastern europe, where I had car with manual gearbox (and with ceramic clutch, turbo, etc rough stuff under hood keeping you busy in traffic =)). I quickly get used to do smooth driving and continue to do it here in usa too on my automatic trans car.
why exactly do you need to switch gears? Just leave it in first. And engage the clutch when you are stopped.
If you're stuck in traffic for a long time, your leg engaging the clutch can get very tired. So you're constantly switching to neutral to rest your leg.
It's also not uncommon for traffic to go from stopped, to fast enough to warrant 2nd gear, back to stopped.
It's also not uncommon for traffic to go from stopped, to fast enough to warrant 2nd gear, back to stopped.
In my experience that is not the case. Specifically because jams are waves not just slow moving traffic. A gap will open up and quickly I can be in the 3rd gear to catch up. Of course as soon as I do the flow stops again. I could just creep forward in 1st and let the rest of the flow fill in front of me...
Manual transmissions are definitely hell during rush hour... but doesn't seem to affect people contributing to the waves in my experience.
Manual transmissions are definitely hell during rush hour... but doesn't seem to affect people contributing to the waves in my experience.
you will ruin your clutch bearing way faster. it's much better to keep constant speed (for engine/gearbox and for traffic in general). plus - you can't drive on highway on 1st gear. you still need to switch to upper gears.
Hm, just so you know, never drive in first. That's just the one to 'start'. Either, you'll kill your engine too early.
Engaging the clutch every 10 meters is what is irritating. That's the point !
Where I live there's something called 'block driving' (I haven't found a better translation for the Dutch word 'blokrijden'). On busy summer days, when the highway to the coast is jammed, a police car will block the highway, then drive at a constant speed (and slower than the maximum speed), with no one being allowed to pass the police car. Apparently this helps to resolve the traffic waves.
The California Highway Patrol appears to do this in Southern California as well. I've seen a patrol car start weaving between two lanes, then three, weaving more and more until it's blocking all lanes of traffic like a weavy pace car.
It's called "running a break", and I've only seen it used to clear debris or disabled cars out of lanes, or so that a construction crew can close a lane. It'll freak you out the first time a cop car swerves in front of you across 5 lanes of traffic.
I've definitely seen it used in both Nor Cal and So Cal to slow traffic down. They do it on I-5 fairly often during rush hour, of all times.
They do that to slow or stop traffic when there's debris or an accident ahead.
That's actually one of the solutions suggested by the author. A rolling blockcade of police cars in each lane to regulate the flow.
An oldie, but a goodie.
I base my commuting style on this guys articles. Drive slightly slower than everyone else and let large spaces grow in front of your car. It's a lot harder than it sounds (for me anyway) but when I get it right, it makes my drive much more enjoyable.
People that just HAVE to drive as fast as possible will go around you (you should never do this in the left lane) and everyone else will sort of get in line after you... it looks a bit like those nascar groups where all the cars go exactly the same speed.
I base my commuting style on this guys articles. Drive slightly slower than everyone else and let large spaces grow in front of your car. It's a lot harder than it sounds (for me anyway) but when I get it right, it makes my drive much more enjoyable.
People that just HAVE to drive as fast as possible will go around you (you should never do this in the left lane) and everyone else will sort of get in line after you... it looks a bit like those nascar groups where all the cars go exactly the same speed.
This space also enables you to time the lights, so you do less accelerating/decelerating, and increases your buffer for breaking, so driving is safer and less stressful.
Also somewhat related, if there's a slow vehicle in front of you when you're going down the on-ramp to the interstate -- slow down even more so you have many car lengths to merge.
Nobody else I've ridden with will do this (I've suggested it). Instead, they tailgate the slow car, curse like mad, and then almost cause a wreck when the try to pass the slow car in full-speed traffic as soon as they enter the interstate.
If you leave enough space you can easily get up to interstate speed and pass them quickly and effectively.
Nobody else I've ridden with will do this (I've suggested it). Instead, they tailgate the slow car, curse like mad, and then almost cause a wreck when the try to pass the slow car in full-speed traffic as soon as they enter the interstate.
If you leave enough space you can easily get up to interstate speed and pass them quickly and effectively.
Except that people who want to go faster than you will pass you and get in front of you. This leads you to either keep slowing down to maintain the space or start shrinking the space.
Yes, many people will pass you and go in front. That's not such a big deal since many of them switch into yet another lane (Some will even exit the freeway only to immediately re-enter) as they try to gain even half a car-length on everyone else.
I don't feel like competing with them.
Personally, I'm not trying to fix traffic for everyone. I'm selfishly trying to make my own commute as pleasant as possible. By following the advice in this old article I've managed to greatly improve my own drive, and I find the amount of time I spend in the slow pockets of traffic greatly reduced.
I don't feel like competing with them.
Personally, I'm not trying to fix traffic for everyone. I'm selfishly trying to make my own commute as pleasant as possible. By following the advice in this old article I've managed to greatly improve my own drive, and I find the amount of time I spend in the slow pockets of traffic greatly reduced.
I'm concerned that when cars doing this are the minority, with other traffic constantly going around them, they just become an obstacle in traffic. If you inspire other cars to change lanes to pass you, because you're intentionally driving slower, you may be making traffic less safe.
This is a fair concern. I have not seen this in practice, though, and it might be a matter of the part of the world where I drive vs where other people drive. But let's cut to the chase with how the system works:
You are not supposed to be driving slower. You are supposed to be driving in average speed with the traffic. You may have had to slow down in the first place to do this. If you are just starting out, a good rule of thumb is to just leave space between you and the vehicle in front of you; keep pace.
The key is to maintain enough space between you and that vehicle that you can
(1) allow people to freely pass through (they are going to do something crazy to do it anyway if they do not have the space)
(2) absorb traffic waves
It is likely you will not be able to do #2 consistently. But you can let off your gas and not hit the break. Hitting the break is an instantaneous warning signal to people behind you, causing something of a reflex for them to also hit the brake. You are trying to avoid the brake-light wave. Letting off easy generally does not cause as much reaction.
What if you end up in a traffic jam anyway? Leave space anyway. It does help.
Aren't more accidents are caused by people getting panicky as they try to cross lanes of traffic that are closed to them? They force their way in or speed up to get around a bunch of people?
It is all about leaving that space so they are comfortable. Everything begins to move faster. And you are more relaxed in your driving because you are not freaking out at what is going on in front of you, allowing you the freedom to react as necessary to all the other kinds of problems traffic can bring.
Intentionally driving slower over a long distance is a misapplication of the principles. As the article points out, it is all about the average speeds. Frankly, very rarely does anyone get "pissed", and all they do is pass around you. And then they end up hitting their brakes and shifting out quickly. Passing != bad thing; we are not trying to win a race here. I have never been honked at.
You are not supposed to be driving slower. You are supposed to be driving in average speed with the traffic. You may have had to slow down in the first place to do this. If you are just starting out, a good rule of thumb is to just leave space between you and the vehicle in front of you; keep pace.
The key is to maintain enough space between you and that vehicle that you can
(1) allow people to freely pass through (they are going to do something crazy to do it anyway if they do not have the space)
(2) absorb traffic waves
It is likely you will not be able to do #2 consistently. But you can let off your gas and not hit the break. Hitting the break is an instantaneous warning signal to people behind you, causing something of a reflex for them to also hit the brake. You are trying to avoid the brake-light wave. Letting off easy generally does not cause as much reaction.
What if you end up in a traffic jam anyway? Leave space anyway. It does help.
Aren't more accidents are caused by people getting panicky as they try to cross lanes of traffic that are closed to them? They force their way in or speed up to get around a bunch of people?
It is all about leaving that space so they are comfortable. Everything begins to move faster. And you are more relaxed in your driving because you are not freaking out at what is going on in front of you, allowing you the freedom to react as necessary to all the other kinds of problems traffic can bring.
Intentionally driving slower over a long distance is a misapplication of the principles. As the article points out, it is all about the average speeds. Frankly, very rarely does anyone get "pissed", and all they do is pass around you. And then they end up hitting their brakes and shifting out quickly. Passing != bad thing; we are not trying to win a race here. I have never been honked at.
"But you can let off your gas and not hit the break. Hitting the break is an instantaneous warning signal to people behind you, causing something of a reflex for them to also hit the brake."
...As long as you're careful about doing this, of course. If the people behind you aren't paying enough attention to notice a slow decrease in speed (and can't see the reason you're slowing down), they'll be hitting the brakes hard to slow down when they're suddenly too close.
In hilly city driving (hi, SF), I will actually intentionally use my brakes to signal to the people behind me I'm trying to slow down, because there's often not enough space to notice when your line of site effectively stops at the next intersection's brief period of flat road. And yeah, this behavior was inspired by seeing someone rear-ended right behind me.
...As long as you're careful about doing this, of course. If the people behind you aren't paying enough attention to notice a slow decrease in speed (and can't see the reason you're slowing down), they'll be hitting the brakes hard to slow down when they're suddenly too close.
In hilly city driving (hi, SF), I will actually intentionally use my brakes to signal to the people behind me I'm trying to slow down, because there's often not enough space to notice when your line of site effectively stops at the next intersection's brief period of flat road. And yeah, this behavior was inspired by seeing someone rear-ended right behind me.
Yeah, I am sure I am not alone in despising tailgating. It is the exact opposite of what we are talking about in this thread, a product of impatience and bad assumptions. You simply cannot stop some people from hitting the brakes repeatedly. You can just work to reduce it by not causing the reflex response in most situations.
I also refuse to be pushed by people who ride my tail; I maintain my speed and ignore them (which is oodles better than slowing down to teach them a lesson, which actually does the other thing I was warning against here, causing a ripple in the traffic). It is my rebellious nature against their several ton weapon.
I also refuse to be pushed by people who ride my tail; I maintain my speed and ignore them (which is oodles better than slowing down to teach them a lesson, which actually does the other thing I was warning against here, causing a ripple in the traffic). It is my rebellious nature against their several ton weapon.
Trying to drive competitively in a traffic jam is always unsafe. Actually, at least around Seattle I haven't noticed traffic "constantly" going around me as I do this. By making it easier for people to merge into the lane in front of me I'm actually making it a lot safer for them.
They honestly don't go around you that much in my experience. When I've tried it, people seem to usually fall in line behind you - I think they're not really sure what's going on.
Except that by doing this you can (in theory) make traffic actually move faster, so there will ultimately be less passing.
In the real world, where I have tried this, this doesn't turn out to be a real problem. It happens a little (not as much as you'd think, since traffic is jammed to the left and right of you) but by and large I'm consistently able to keep several car lengths open in front of me, even as people merge in from adjacent lanes.
I used to do this every once in a while. One thing to be aware of, are large trucks behind you at the top of hills. They tend to want to increase speed going down hills to use their velocity to climb the next. It's probably a good idea to accommodate this.
Interesting observation is that what TFA calls the "cheaters", ie those who drive to the end of their lane before merging at the last minute, may actually be doing the right thing. See Tom Vanderbilt talk about it here http://www.vimeo.com/6779064.
If you're interested in this there's a nice longer interview with Tom at Streetfilms http://www.streetfilms.org/tom-vanderbilt-talks-traffic or an hour long Google talk.
If you're interested in this there's a nice longer interview with Tom at Streetfilms http://www.streetfilms.org/tom-vanderbilt-talks-traffic or an hour long Google talk.
He doesn't say why in the short one (I haven't watched the long one). Late mergers are definitely bad in some situations - for example, when they are merging into a slow-moving turnoff lane, blocking a whole lane of ongoing traffic.
He goes into the research a bit more in the Google talk and you see where he pulls the magic "15% improvement" from. Also he has a book (which I haven't read) called Traffic so he might explain it more or cite studies there.
I agree though that it doesn't really work in all situations. Tom uses the example of two lanes merging into one for roadworks. Maybe some situations where it doesn't work are an example of poor road design by traffic engineers?
I agree though that it doesn't really work in all situations. Tom uses the example of two lanes merging into one for roadworks. Maybe some situations where it doesn't work are an example of poor road design by traffic engineers?
I had the good fortune to do a three month internship in Seattle last spring. And I have to say - after growing up in Dallas, now living in Florida, and seeing traffic in other places... Seattle drivers are unique.
I've seen this [appear to] work in Seattle. While I was there, I tried it, and it appeared to work.
However, while I lived in Dallas, I was aware of this idea, and tried it there - and no way. People cut in, people tailgated - it completely doesn't work.
So I think it partially depends on the nature of the city's drivers. And there is something special about Seattle.
I've seen this [appear to] work in Seattle. While I was there, I tried it, and it appeared to work.
However, while I lived in Dallas, I was aware of this idea, and tried it there - and no way. People cut in, people tailgated - it completely doesn't work.
So I think it partially depends on the nature of the city's drivers. And there is something special about Seattle.
I live and work in DC. I go to Dallas at least once a year and drive every day during the week and weekend. I agree this would be impossible in Dallas traffic. It doesn't feel as intentionally aggressive as DC traffic, instead it's like everyone in Dallas can't take their foot off the accelerator even if they wanted to. It's hard enough finding a space between two cars to merge, you usually have to just go for it and hope the rear car can find his brakes.
It definitely took me a while after moving away from Dallas to change some of my driving habits.
I still definitely change lanes more than most drivers around here - although I do my best not to cut anyone off, and I actually let drivers in here... something definitely not done often in Dallas.
It also helps that I went from a 90 minute commute (each way) to usually a 10-15 minute commute here (depending on where I've worked). Smaller towns do have some benefits...
I still definitely change lanes more than most drivers around here - although I do my best not to cut anyone off, and I actually let drivers in here... something definitely not done often in Dallas.
It also helps that I went from a 90 minute commute (each way) to usually a 10-15 minute commute here (depending on where I've worked). Smaller towns do have some benefits...
The solution to traffic jams is to not leave transportation in the hands of clueless, distracted, reckless drivers. The solution is fast, reliable, ubiquitous public transit.
Public transit is impractical and uneconomic in many areas. The real solution is smart roads and computer-driven electric cars.
Perhaps, but in the context of the article, traffic jams only exist because of commuters. The interstate & highway systems were not designed for commuters and should not be used for them. While I think computer-driven cars will be a boon to the environment and economy, the capital investment needed is pretty fantastic, which is going to be some decades off.
In fact, a real solution to this problem that could be applied in the design of our current urban landscape would be a multi-pronged effort to spread out the commuter traffic. Alternating work and school hours could widen commuting hours and distribute load across all commuter infrastructure. Increased levels of telecommuting would also contribute to this. This would be a sort of supply-side fix to commuter congestion. Local or regional governments could create incentives to encourage these changes.
In fact, a real solution to this problem that could be applied in the design of our current urban landscape would be a multi-pronged effort to spread out the commuter traffic. Alternating work and school hours could widen commuting hours and distribute load across all commuter infrastructure. Increased levels of telecommuting would also contribute to this. This would be a sort of supply-side fix to commuter congestion. Local or regional governments could create incentives to encourage these changes.
The first-generation interstate highway system wasn't designed for commuters, but everything added or upgraded in the past 40 years has been.
Many new luxury cars already come with limited computer driving, in the form of adaptive cruise control. The capital investment is small and rapidly dropping, and just that one innovation could deliver a major reduction in traffic congestion.
http://www.springerlink.com/content/p56714553g82r2h7/
the capital investment needed is pretty fantastic
The intersection of the set of places that get traffic jams and the set of places in which public transit is impractical and uneconomic is very small.
In the US most large suburban and exurban traffic areas have traffic jams. Those are also places where public transit is impractical for most people. Or at least people aren't willing to make the sacrifices in time and money to make public transit work. People like to be able to go wherever they want whenever they want without waiting in the rain for a bus that never comes.
The problem with personal automobiles right now is that they are dangerous, slow, expensive, and have a huge carbon impact. We can find technical solutions to all those problems without restricting everyone's freedom of movement by forcing them into public transit.
The problem with personal automobiles right now is that they are dangerous, slow, expensive, and have a huge carbon impact. We can find technical solutions to all those problems without restricting everyone's freedom of movement by forcing them into public transit.
My solution required that public transit be fast, reliable and ubiquitous. This can easily be done. I've personally experienced it in Germany. Good public transit is freeing, not restricting.
Since I drive a car, every time I go out with my wife, I have to be careful how much alcohol I consume. If I had a train or bus to take, I could drink however much I wanted.
Since I drive a car, if I want to walk around town, I have to return to my car before being able to head home. If there was public transit, I could just go to the nearest station and connect from there.
Since I drive a car, I have to pay to park if I go downtown (and hunt for a parking spot).
Since I drive a car, I have to inconvenience a friend or pay for a taxi whenever I go to the airport.
Since we drive cars, my wife and I can't meet somewhere after work unless we we're willing to have two cars.
Since I drive a car, I have to pay for gas and maintenance, and there is no good alternative if my car breaks down. A bus line can just add another bus, or reduce the number of stops. The route doesn't just shut down.
Since I drive a car, every time I go out with my wife, I have to be careful how much alcohol I consume. If I had a train or bus to take, I could drink however much I wanted.
Since I drive a car, if I want to walk around town, I have to return to my car before being able to head home. If there was public transit, I could just go to the nearest station and connect from there.
Since I drive a car, I have to pay to park if I go downtown (and hunt for a parking spot).
Since I drive a car, I have to inconvenience a friend or pay for a taxi whenever I go to the airport.
Since we drive cars, my wife and I can't meet somewhere after work unless we we're willing to have two cars.
Since I drive a car, I have to pay for gas and maintenance, and there is no good alternative if my car breaks down. A bus line can just add another bus, or reduce the number of stops. The route doesn't just shut down.
I've tried this in Boston. Mass-holes will not stand for you to screw with their traffic jams.
I agree that this doesn't work well around Boston. My opinion is that the fluidity of traffic, ie. lane changing, doesn't break down at low speeds in Boston. If you let a cars length open in front of you it will fill up with a car. I tend to think that this makes efficient use of the pavement available and tends for a traffic flow that is as maximal as possible but I don't have any evidence about that.
If efficient use of pavement means park the most cars on it Then by all means fill every available space. Safe following distance increases with the square of the speed so higher average vehicle speeds means the road carries less traffic. The road moves the most cars around 30mph, so if traffic slows below 30 it will crash to 0mph
Cool! What is the science backing this? Is it coming out of studies or some theoretical modeling? I've been wondering what the most efficient speed for moving traffic was on a typical highway for a while.
[deleted]
Google on "Fundamental diagram" of traffic, or http://en.wikipedia.org/wiki/Fundamental_diagram_of_traffic_... It's a set of graphs. Density plotted against speed, etc. It's old stuff, empirically derived. As flowing cars slowly get closer together on average, drivers slow down a bit for safety, yet with more cars passing per second, so the flow increases. But then as they approach even closer, drivers must greatly slow down because of reaction time issues, even though more cars are packed onto the roads ...and so the slowing dominates the extra cars per mile, and average flow decreases. The peak flow ends up being 30MPH - 40MPH. That flow will most rapidly drain out the backups. I hear that it's a different value in different countries.
But worse is the problem that once everyone slows past the 35MPH hump, traffic becomes unstable, and you get oscillations or standing waves which slow things far more than you might expect.
Rule of thumb (but I've never seen it stated anywhere) 35MPH=51FPS, 3 seconds between cars, gives 150 FEET BETWEEN CARS. Closing up gaps will wreck the max. flow pattern. During congestion, if you start trying to stop others from "cutting you off" or merging ahead, then you're the one causing the jam. (Or to be fair, 30MPH and 2sec gives 90ft spacing, perhaps the bare min.)
Another issue: in 1998 Helbing and Huberman discovered the existence of distinct 'phases' in simulated multi-lane traffic. When all lanes seem to lock together like a moving crystal, that's now called "Synchronous Flow," and gives maximum throughput. But it's on the edge of collapse, and "condensations" are triggered by anyone who tries outrunning neighbors by switching lanes, or who approaches too close and has to tap the brakes. http://www.nature.com/nature/journal/v396/n6713/abs/396738a0...
But worse is the problem that once everyone slows past the 35MPH hump, traffic becomes unstable, and you get oscillations or standing waves which slow things far more than you might expect.
Rule of thumb (but I've never seen it stated anywhere) 35MPH=51FPS, 3 seconds between cars, gives 150 FEET BETWEEN CARS. Closing up gaps will wreck the max. flow pattern. During congestion, if you start trying to stop others from "cutting you off" or merging ahead, then you're the one causing the jam. (Or to be fair, 30MPH and 2sec gives 90ft spacing, perhaps the bare min.)
Another issue: in 1998 Helbing and Huberman discovered the existence of distinct 'phases' in simulated multi-lane traffic. When all lanes seem to lock together like a moving crystal, that's now called "Synchronous Flow," and gives maximum throughput. But it's on the edge of collapse, and "condensations" are triggered by anyone who tries outrunning neighbors by switching lanes, or who approaches too close and has to tap the brakes. http://www.nature.com/nature/journal/v396/n6713/abs/396738a0...
When I don't know anything about a topic I have found Wikipedia is a good place to start
http://en.wikipedia.org/wiki/Traffic_flow
http://en.wikipedia.org/wiki/Traffic_flow
I've tried this in Phoenix with some success. You do get people passing you, but this helps traffic on average. We also have lights at the freeway on ramps which smooth oncoming traffic, but people ignore them until a line forms. I almost got rear-ended once because someone intended to ignore it and I chose to obey it.
If you do this when traffic is not quite jammed, people are far more upset. It's best used when traffic is being forced to actually stop regularly. You will still get people to honk at you and whatnot, especially once a person or two passes you, but I've long since given up expecting most people to understand the things I do.
If you do this when traffic is not quite jammed, people are far more upset. It's best used when traffic is being forced to actually stop regularly. You will still get people to honk at you and whatnot, especially once a person or two passes you, but I've long since given up expecting most people to understand the things I do.
Heh, I didn't realise that it had such an effect, but this is the exact same game I play when caught up in a heavy traffic: the how-long-can-I-go-before-breaking game! ;-)
It could be related to driving a manual and being lazy, but it helps your concentration no end :)
It could be related to driving a manual and being lazy, but it helps your concentration no end :)
No idea why you were at -1; your comment was informative and on topic.
On a side note, I also tend to play that "game" when stuck in slow home-from-holiday traffic over the mountains. Changing speeds all the time while driving manual is such a pain.
On a side note, I also tend to play that "game" when stuck in slow home-from-holiday traffic over the mountains. Changing speeds all the time while driving manual is such a pain.
I've actually spent quite a bit of time pondering this. Here are my completely unscientific conclusions.
Imagine a [moving] wall, on an interstate, moving at 30MPH. No matter what is happening behind this wall, it is impossible to maintain an average speed faster than the wall. You can try any amount of tricks to smooth out traffic, but it will be impossible to ever move past this wall. As long as there is a steady stream of traffic, no car will ever do more than 30MPH until this moving wall gets out of the way.
So now let's, more realistically, replace the wall with a bunch of slow drives, and ask 2 important questions:
1. How to get out of this situation? -- We want these drivers to all SPEED UP! It's really as simple as this. Until these bottleneck drivers move out of the way, you can only smooth out traffic, but never increase the speed.
2. How to avoid this problem in the first place? -- In general, there will be some bottleneck. After too many cars are going through this bottleneck at once, there will be slowdown. Ideally, these bottlenecks should be identified and no more than the maximum amount of cars at a time should enter the bottleneck to decrease the speed of traffic.
Of course, that's easier said than done, but I think the important thing to take away from my ramblings is this:
The best way to get rid of a traffic jam is: if you are in the front of the pack and have a chance to accelerate, you should do so as quickly as possible. If everybody were to do this, average speed could then be increased.
Imagine a [moving] wall, on an interstate, moving at 30MPH. No matter what is happening behind this wall, it is impossible to maintain an average speed faster than the wall. You can try any amount of tricks to smooth out traffic, but it will be impossible to ever move past this wall. As long as there is a steady stream of traffic, no car will ever do more than 30MPH until this moving wall gets out of the way.
So now let's, more realistically, replace the wall with a bunch of slow drives, and ask 2 important questions:
1. How to get out of this situation? -- We want these drivers to all SPEED UP! It's really as simple as this. Until these bottleneck drivers move out of the way, you can only smooth out traffic, but never increase the speed.
2. How to avoid this problem in the first place? -- In general, there will be some bottleneck. After too many cars are going through this bottleneck at once, there will be slowdown. Ideally, these bottlenecks should be identified and no more than the maximum amount of cars at a time should enter the bottleneck to decrease the speed of traffic.
Of course, that's easier said than done, but I think the important thing to take away from my ramblings is this:
The best way to get rid of a traffic jam is: if you are in the front of the pack and have a chance to accelerate, you should do so as quickly as possible. If everybody were to do this, average speed could then be increased.
But note that there aren't any slowpokes here, instead, every single car is blocked by the car ahead of them. The people behind you think that you are the slowpoke driver. But nothing is blocking the traffic, instead the average speed of the long column of cars is determined by the spacing between cars, and that spacing is determined by psychology.
In light traffic, some people go far faster than average, but nobody tries to stop them. When we arrive at heavy congestion, don't we suddenly decide to close up ranks to prevent aggressive drivers from passing, stop them from "cutting us off?" If everyone habitually blocks the speeders, then it means we've compressed the traffic pattern past the peak of maximum flow, and pushed it into the unstable realm of stop/go oscillations and standing waves or "ghost jams."
Want jams to vanish? Then do as the pro truckers do and just freaking back off. Happily encourage other cars to merge ahead. (They're not "cutting you off," there's no such thing as "cutting you off." They're just trying to merge into the adjacent lane!) If traffic momentarily slows way down, everyone just make sure to keep an open space that allows merging, and you'll find that it speeds right back up again.
In light traffic, some people go far faster than average, but nobody tries to stop them. When we arrive at heavy congestion, don't we suddenly decide to close up ranks to prevent aggressive drivers from passing, stop them from "cutting us off?" If everyone habitually blocks the speeders, then it means we've compressed the traffic pattern past the peak of maximum flow, and pushed it into the unstable realm of stop/go oscillations and standing waves or "ghost jams."
Want jams to vanish? Then do as the pro truckers do and just freaking back off. Happily encourage other cars to merge ahead. (They're not "cutting you off," there's no such thing as "cutting you off." They're just trying to merge into the adjacent lane!) If traffic momentarily slows way down, everyone just make sure to keep an open space that allows merging, and you'll find that it speeds right back up again.
Yes, absolutely. This is my experience as well. Related: http://news.ycombinator.com/item?id=785498
Somewhat different from the commuter-oriented topic of the article, I've seen attempts by truckers to enforce a similar pattern in construction zones (traffic reduced by one or more lanes) on long stretches of highway: In a situation where one lane has to merge because it is closed in the distance, the "nice" drivers all merge far ahead of time, while the aggressive drivers attempt to go all the way to the end of the lane and then merge ahead of everyone, causing the kind of grinding gears described in the article. To combat this, a couple of big rigs driven in parallel in the open lane and the lane that is closed ahead block all traffic from passing. This prevents the aggressive drivers from attempting to merge at the last second, smoothing out the wave. I've seen this happen several times on cross-country trips; I wonder if the truckers coordinate over radio or just choose to do it independently.
On a related note, I wonder if "lane closed ahead" signs placed too far ahead actually make this problem worse, since many drivers will immediately merge out of the closing lane far ahead of time, causing a wall of traffic if the front of the line has to slow down for aggressive last-second merges.
On a related note, I wonder if "lane closed ahead" signs placed too far ahead actually make this problem worse, since many drivers will immediately merge out of the closing lane far ahead of time, causing a wall of traffic if the front of the line has to slow down for aggressive last-second merges.
I remember reading this article while back: "Traffic jam mystery solved by mathematicians".
http://www.physorg.com/news117283969.html
So now when I'm in a jam, I just slow down instead of engaging the speedup, break pattern. Haven't looked behind me though to see if I had any effect on the traffic behind me.
So now when I'm in a jam, I just slow down instead of engaging the speedup, break pattern. Haven't looked behind me though to see if I had any effect on the traffic behind me.
In Melbourne, Australia, a similar concept was used to ease congestion entering freeways. We had a peak-hour problem where cars would flood the entry ramps, but struggle to merge with the existing freeway traffic - this caused people to brake/slow down which resulted in major jams.
To alleviate this issue "there are traffic lights at some freeway entrances to control the flow of vehicles onto the freeway when the traffic is heavy. When operating, the lights will change quickly, so that when the light is green only one vehicle in each lane will be able to enter the freeway." (taken from VicRoads website)
The lights basically cycle from red to green every 2 seconds. That's enough to regulate the flow onto the freeway and minmises jams on the entry ramp and at the merge point between the freeway and entry ramp.
To alleviate this issue "there are traffic lights at some freeway entrances to control the flow of vehicles onto the freeway when the traffic is heavy. When operating, the lights will change quickly, so that when the light is green only one vehicle in each lane will be able to enter the freeway." (taken from VicRoads website)
The lights basically cycle from red to green every 2 seconds. That's enough to regulate the flow onto the freeway and minmises jams on the entry ramp and at the merge point between the freeway and entry ramp.
In fact, here is a YouTube video of the lights in operation:
http://www.youtube.com/watch?v=YFrEd8qSVCc
This is used extensively in the SF bay area.
The problem with slowing down miles in front of a traffic jam is that those who normally gets of before that space now has to suffer too.
In addition, most people would cut you of if you drove slower than the maximum speed.
In addition, most people would cut you of if you drove slower than the maximum speed.
So, what would happen on major interstates if highway patrols kept a steady pace? Is that a viable solution? Wouldn't they eventually run up on another wave of cars and ruin everything?
I would be really interesting to see if this actually improved interstate bandwidth during rush hours. But even more interesting, I bet a good portion of drivers would get upset at the fact that there are huge, unused gaps. I wouldn't be surprised to hear from people who think it is grossly more inefficient than regular old traffic jams...
I would be really interesting to see if this actually improved interstate bandwidth during rush hours. But even more interesting, I bet a good portion of drivers would get upset at the fact that there are huge, unused gaps. I wouldn't be surprised to hear from people who think it is grossly more inefficient than regular old traffic jams...
The success of this technique can't be accurately measured by the driver who's trying "smooth" out the waves. It needs to be witnessed from outside of traffic. It usually just moves the problem to behind the "helpful" driver as other drivers can very easily continue to drive competitively and recreate the effect. Even if he's successful in removing the "wave", it's just by decreasing the average speed of traffic.
Please don't try this in the left lane.
Please don't try this in the left lane.
Actually, if the wave is successfully removed average traffic speed should increase. In fact, the whole post is an argument about ways to improve average traffic speeds.
He basically advocates estimating how fast traffic is really going, and going at that speed. Instead of reaching a bottleneck quickly, you should slow down appropriately in advance so that you never have to actually stop. Note that you (and the people behind you) still get through the bottleneck at the same speed, so there is no cost to you (or them), just less braking and accelerating.
For what it's worth, some freeway entrances near me (Melbourne, Australia) have traffic lights which rate-limit entry onto the freeway in peak hours. This is exactly the same as what this author is trying to do; by rate-limiting cars at entry, they're not actually slowing them down, since it increases average on-freeway speeds.
He basically advocates estimating how fast traffic is really going, and going at that speed. Instead of reaching a bottleneck quickly, you should slow down appropriately in advance so that you never have to actually stop. Note that you (and the people behind you) still get through the bottleneck at the same speed, so there is no cost to you (or them), just less braking and accelerating.
For what it's worth, some freeway entrances near me (Melbourne, Australia) have traffic lights which rate-limit entry onto the freeway in peak hours. This is exactly the same as what this author is trying to do; by rate-limiting cars at entry, they're not actually slowing them down, since it increases average on-freeway speeds.
[deleted]
That's exactly why nobody would play along even if they knew. Big trucks eventually do that because it's painful for them to do the gears 1,2,3 constantly, they stay in second or third and just slow down the whole thing.
Here is the thing where it falls short though:
the guy at the front riding the wave really slow to "help lane locks" will also get merging traffic many many time right in front of him (people taking advantage of the free space), as a result, it won't help that lane but only make it worse if you're stuck behind such driver (or truck).
So if everyone stuck to their lanes, didn't change unless extremely necessary, and played the wave-canceling technique, it would work.
In other words, this will work when cars will be driven by computers hooked together via apis and maybe a traffic controller. I'm not signing for the beta.
Here is the thing where it falls short though:
the guy at the front riding the wave really slow to "help lane locks" will also get merging traffic many many time right in front of him (people taking advantage of the free space), as a result, it won't help that lane but only make it worse if you're stuck behind such driver (or truck).
So if everyone stuck to their lanes, didn't change unless extremely necessary, and played the wave-canceling technique, it would work.
In other words, this will work when cars will be driven by computers hooked together via apis and maybe a traffic controller. I'm not signing for the beta.
Actually, the fact that people in the middle lane are taking up his 'free' space helps the long term traffic.
The main cause of traffic wave is from someone stopping too abruptly, eg. if someone changes lane in tight traffic, he forces the other person to slow down too fast, which begins the wave.
If you allow more people to get in front of you in a smooth manner because you have given yourself a lot of distance, then there will be less 'cutting off' slow downs from the middle lane guys, which in turn causes less cutting offs in the right lane.
How much does it hurt over your entire commute to let even 100 cars in front of you? You'll be 500 meters later to your destination, what's that at 30kph...1 minute more? That's the worst case scenario. The normal case is you'll get there quicker because you've raised the average speed of the entire traffic wave.
The main cause of traffic wave is from someone stopping too abruptly, eg. if someone changes lane in tight traffic, he forces the other person to slow down too fast, which begins the wave.
If you allow more people to get in front of you in a smooth manner because you have given yourself a lot of distance, then there will be less 'cutting off' slow downs from the middle lane guys, which in turn causes less cutting offs in the right lane.
How much does it hurt over your entire commute to let even 100 cars in front of you? You'll be 500 meters later to your destination, what's that at 30kph...1 minute more? That's the worst case scenario. The normal case is you'll get there quicker because you've raised the average speed of the entire traffic wave.
Absolutely! I've thought about this so many times... what is 5 seconds for you (allowing someone to merge in front of you) would translate to much much faster commute to _everyone_ else. It is all about the balance between my personal greed and what's better for the common good (if only we could solve this on _and_ off the road).
Where I live there is terrible traffic... and I've contemplated causes and solutions many a mind-numbing commute. I realized we behave differently when we are behind the wheel... Very few people would behave or maneuver the same if it where lines of people instead of cars. That is why your best chance to merge is to make eye contact with the other driver - if they recognize you as another human not just another vehicle than they are much more likely to move over or make space.
When I drive (during rush hour) I suffer a lot to justify my actions. What I have settled on... is a simple rule: In any situation the person who is in the wrong is the one who has contributed to the impediment of the overall flow of traffic. This comes back to what zepolen says (and I agree with). If we could ever make the connection that what's good for my fellow (wo)man is good for me too... we would be so much better off in general.
Where I live there is terrible traffic... and I've contemplated causes and solutions many a mind-numbing commute. I realized we behave differently when we are behind the wheel... Very few people would behave or maneuver the same if it where lines of people instead of cars. That is why your best chance to merge is to make eye contact with the other driver - if they recognize you as another human not just another vehicle than they are much more likely to move over or make space.
When I drive (during rush hour) I suffer a lot to justify my actions. What I have settled on... is a simple rule: In any situation the person who is in the wrong is the one who has contributed to the impediment of the overall flow of traffic. This comes back to what zepolen says (and I agree with). If we could ever make the connection that what's good for my fellow (wo)man is good for me too... we would be so much better off in general.
I agree in the situation where all other drives on the road are equally intelligent and paying attention when they drive.
Sadly, in the area I drive in, many drivers are constantly paying more attention to their phone than the road. Those drivers cause all of the traffic problems I see. They likely contribute to many of the accidents as well. They will end up leaving huge gaps in front of them at the expense of traffic behind them even when traffic ahead of them is moving smoothly and quickly.
The cost of letting cell phone drivers in front of you can be many minutes to your commute per each driver. Add a few minutes for each traffic light or merge lane that you will spend behind the inattentive drivers.
In a 5 mile commute, following the flow of inattentive drivers can add 45 minutes to my drive. Attentive driving and following the flow of other "aggressive" drivers can make it a 10 minute drive total.
So what I have actually found helps, in a real world scenario, not a fictional one where all drivers are equal, is trying to identify and cooperate with other "aggressive" drivers helps the group of aggressive drivers get through traffic efficiently and gives the cell-phone drivers plenty of time to concentrate on their conversations.
Sadly, in the area I drive in, many drivers are constantly paying more attention to their phone than the road. Those drivers cause all of the traffic problems I see. They likely contribute to many of the accidents as well. They will end up leaving huge gaps in front of them at the expense of traffic behind them even when traffic ahead of them is moving smoothly and quickly.
The cost of letting cell phone drivers in front of you can be many minutes to your commute per each driver. Add a few minutes for each traffic light or merge lane that you will spend behind the inattentive drivers.
In a 5 mile commute, following the flow of inattentive drivers can add 45 minutes to my drive. Attentive driving and following the flow of other "aggressive" drivers can make it a 10 minute drive total.
So what I have actually found helps, in a real world scenario, not a fictional one where all drivers are equal, is trying to identify and cooperate with other "aggressive" drivers helps the group of aggressive drivers get through traffic efficiently and gives the cell-phone drivers plenty of time to concentrate on their conversations.
Yeah, I always thought that the only way to prevent traffic jams would be to remove the human factor entirely. Makes me wonder why people fight so much against this, I would love to be able to read while going to work (when I don't catch the bus as usual).
I would love seeing fewer drivers in cars already reading on their way to work. Educating human drivers may be just as good as replacing them.
I'm not sure if you really got the point of the article: The wave happens because everyone wants to be {X} behind the person in front (usually because they desperately want to block anyone else getting between them and {X}). If you can enforce (for lack of a better word) a constant speed, people can maintain that {X} distance without constant accelerating and braking -- just by coasting at a constant speed.
>Even if he's successful in removing the "wave", it's just by decreasing the average speed of traffic.
How would it decrease the average speed in any practical way? Secondly, it would dramatically reduce the energy consumption of the waves (accelerating and braking constantly) and wear and tear on vehicles. The net benefit of optimizing highway traffic -- in real environmental and economic benefits -- is significant.
>Please don't try this in the left lane.
The left lane has no meaning during congestion. There is no "passing" when the highway is clogged. And yes, this is actually the law in many places. One of the biggest causes of highway inefficiency are the self-important (but usually going nowhere) people who pretend that by driving aggressively, they should be allowed through the congestion.
>Even if he's successful in removing the "wave", it's just by decreasing the average speed of traffic.
How would it decrease the average speed in any practical way? Secondly, it would dramatically reduce the energy consumption of the waves (accelerating and braking constantly) and wear and tear on vehicles. The net benefit of optimizing highway traffic -- in real environmental and economic benefits -- is significant.
>Please don't try this in the left lane.
The left lane has no meaning during congestion. There is no "passing" when the highway is clogged. And yes, this is actually the law in many places. One of the biggest causes of highway inefficiency are the self-important (but usually going nowhere) people who pretend that by driving aggressively, they should be allowed through the congestion.
As a side note, I remember reading articles on this author's webpage almost 15 years ago. Some awesome stuff from a long-time netzen!
http://amasci.com
http://amasci.com
A side effect of doing this is that it is much more fuel efficient to not have to go into a cycle of breaking and accelerating again.
[deleted]
Maybe the author never heard anything about green waves.
http://en.wikipedia.org/wiki/Green_wave
Green waves are a pet peeve of mine. They've tried to implement these where I lieve... a spectacular failure. Green waves only work when there is NO traffic. Speed is regulated and the flow moves fine. During rush hour they are a disaster. Every light is backed up to previous. My light turns green, then I have to wait 10 seconds for the next light to turn green and the entire line of traffic to move, before I can advance. This usually results in a stop at each light. A much better solution is what I remember from NYC: all the lights turn green at once, all the traffic moves.
Thats what those changable speed limit signs on the motorway are trying to achieve.
(I've also seen markings to keep cars 10 metres apart on some roads).
(I've also seen markings to keep cars 10 metres apart on some roads).
Old.
I'm telling you that, because as a frequent driver (well, today I drive a bike but still) in Paris, and kind of very observant, I clearly see that most people are not doing what these drivers do in this experiment. Most of the time, everybody will let a huge space between the car behind them in order to avoid changing the gears too frequently.
On the contrary, on automatic cars (I had one and drove another for 6 months in Canada), that's easier to go & stop & go & stop & go & stop, etc...
Not sure if it's related, but I think it is, in a small proportion.
edit: my english